2009 Chemistry Unit 3 Exam Questions and Suggested Solutions

[lukeperry91]

Stop posting on this thread if you don't want to discuss the exam hard.

[Ilovemathsmeth]

To hard: Can you please stop being so harsh? Some people are pretty upset on this site. You're not being very considerate.

[littlecherry25]

H2
DOES NOT REACT WITH ALKANES.......

alkanes are unreactive...that's why you have to react them with Cl2 first before you can react them with NaOH

having said that...how much more will it NOT react with H2??

[NE2000]

for the h2 gas multiple choice thingy

realise the stuff we learn is really simplified down. As if your ever going to get a gas chromatogram with just one clear peak. Anyways, the reason inherts gases are used is so they don't react with the sample. However, i think the question deliberately mentions a "straight chain alkane" to test if we realise H2 gas doesn't react with it (or so says my chem text)

They question may also have deliberately mentioned 'straight-chain alkane' so that we know that there are no polar groups to distort the order of boiling points we deduce. Anyway, it is all speculation at this stage, I think the only thing we have concluded was that it could go either way

[lukeperry91]

The samples will not be pure alkanes, therefore, impurities might react with H2

[turley]

anyways.. what do u think the A+ mark is for this year? was 87% last year 

[lukeperry91]

maybe 83-85%??

[Mao]

Mao would have got another 50 in the bag, change the rules VCAA!! And another in 2010 ..etc


It would be cool if you can repeat subjects, but unfair maybe.

You can repeat subjects with no penalty, just takes longer time really.

[Mao]

hydrogen is highly flammable - so  on that fact i didnt put hydrogen as it wouldnt be smart putting a flamable gas into a hot oven.... what do you guys think?

Very interesting! Any thoughts Mao?

Flammable = combustion in oxygen. There's no oxygen in the column [but if they were oxygen containing hydrocarbons, it would indeed be dangerous]

H2 is otherwise unreactive for this situation. It may not be the best choice, but it certainly 'could have been used'

[tomygun_123]

ey Mao, you sure about Qstn 14 of multiple choice?? id belive it to be C, the diagram is a bit tricky...

[Mao]

As for short answer Question 3 c (titration), I just realised I didn't read the question properly. Indeed the question did not specify whether NaOH was in the burette or conical flask. Check first post for additional explanation

[NE2000]

ey Mao, you sure about Qstn 14 of multiple choice?? id belive it to be C, the diagram is a bit tricky...

Sketch II represents an alpha helix: secondary structure

[emo]

any1 got the solutions

[homghomg1]

Hmm I haven't read through everything so maybe this has already been asked, but you didn't include Step 1 in the short answer Q7.
This is CO2 going to C6H12O6
The C goes from oxidation state +4 to 0, and this is therefore a reduction. unless there is something I am missing about "overall" reduction

[NE2000]

any1 got the solutions

first post is Mao's solutions